dyer's-weed

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various plants yielding coloring matter used as dye.

Century Dictionary and Cyclopedia

1. n. The woad, weld, or yellow-weed, Reseda luteola, affording a yellow dye, and cultivated in Europe on that account.
2. n. The woad, Isatis tinctoria.
3. n. Either of the two American goldenrods, Solidago nemoralis and S. rugosa, somewhat used in dyeing. See Solidago.